/* Turn Lab 32bit packed format into displayable rgb. Fast, but very
 * inaccurate: for display only! Note especially that this dithers and will
 * give different results on different runs.
 *
 * The XYZ <-> sRGB transform implemented is this one:
 *
 * http://en.wikipedia.org/wiki/SRGB
 *
 * 5/11/97 Steve Perry
 *	- adapted from old ip code
 * 7/11/97 JC
 * 	- small tidies, added to VIPS
 * 	- LUT build split into separate function
 * 21/9/12
 * 	- redone as a class
 * 	- sRGB only, support for other RGBs is now via lcms
 * 1/11/12
 * 	- faster and more accurate sRGB <-> XYZ conversion
 * 6/11/12
 * 	- added a 16-bit path
 * 11/12/12
 * 	- spot NaN, Inf in XYZ2RGB, they break LUT indexing
 * 	- split sRGB <-> XYZ into sRGB <-> scRGB <-> XYZ so we can support
 * 	  scRGB as a colourspace
 * 10/3/16 Lovell Fuller
 * 	- move vips_col_make_tables_LabQ2sRGB() to first pixel processing
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <stdio.h>
#include <math.h>

#include <vips/vips.h>
#include <vips/internal.h>

#include "pcolour.h"

typedef VipsColourCode VipsLabQ2sRGB;
typedef VipsColourCodeClass VipsLabQ2sRGBClass;

G_DEFINE_TYPE(VipsLabQ2sRGB, vips_LabQ2sRGB, VIPS_TYPE_COLOUR_CODE);

/* 8-bit linear -> sRGB lut.
 *
 * There's an extra element at the end to let us do a +1 for interpolation.
 */
static int vips_Y2v_8[256 + 1];

/* 8-bit sRGB -> linear lut.
 */
float vips_v2Y_8[256];

/* 16-bit linear -> sRGB lut.
 *
 * There's an extra element at the end to let us do a +1 for interpolation.
 */
static int vips_Y2v_16[65536 + 1];

/* 16-bit sRGB -> linear lut.
 */
float vips_v2Y_16[65536];

/* Do our own indexing of the arrays below to make sure we get efficient mults.
 */
#define INDEX(L, A, B) (L + (A << 6) + (B << 12))

/* A set of LUTs for quick LabQ->sRGB transforms.
 */
static VipsPel vips_red[64 * 64 * 64];
static VipsPel vips_green[64 * 64 * 64];
static VipsPel vips_blue[64 * 64 * 64];

/* sRGB to scRGB.
 *
 * @range is eg. 256 for 8-bit data.
 */
static int
vips_col_sRGB2scRGB(int range, float *lut,
	int r, int g, int b, float *R, float *G, float *B)
{
	int maxval = range - 1;
	int i;

	i = VIPS_CLIP(0, r, maxval);
	*R = lut[i];

	i = VIPS_CLIP(0, g, maxval);
	*G = lut[i];

	i = VIPS_CLIP(0, b, maxval);
	*B = lut[i];

	return 0;
}

/* Create the sRGB linear and unlinear luts. @range is eg. 256 for 8-bit luts.
 */
static void
calcul_tables(int range, int *Y2v, float *v2Y)
{
	int i;

	for (i = 0; i < range; i++) {
		float f = (float) i / (range - 1);
		float v;

		if (f <= 0.0031308)
			v = 12.92 * f;
		else
			v = (1.0 + 0.055) * pow(f, 1.0 / 2.4) - 0.055;

		Y2v[i] = VIPS_RINT((range - 1) * v);
	}

	/* Copy the final element. This is used in the piecewise linear
	 * interpolator below.
	 */
	Y2v[range] = Y2v[range - 1];

	for (i = 0; i < range; i++) {
		float f = (float) i / (range - 1);

		if (f <= 0.04045)
			v2Y[i] = f / 12.92;
		else
			v2Y[i] = pow((f + 0.055) / (1 + 0.055), 2.4);
	}
}

static void *
calcul_tables_8(void *client)
{
	calcul_tables(256, vips_Y2v_8, vips_v2Y_8);

	return NULL;
}

void
vips_col_make_tables_RGB_8(void)
{
	static GOnce once = G_ONCE_INIT;

	VIPS_ONCE(&once, calcul_tables_8, NULL);
}

int
vips_col_sRGB2scRGB_8(int r, int g, int b, float *R, float *G, float *B)
{
	vips_col_make_tables_RGB_8();

	return vips_col_sRGB2scRGB(256, vips_v2Y_8, r, g, b, R, G, B);
}

static void *
calcul_tables_16(void *client)
{
	calcul_tables(65536, vips_Y2v_16, vips_v2Y_16);

	return NULL;
}

void
vips_col_make_tables_RGB_16(void)
{
	static GOnce once = G_ONCE_INIT;

	VIPS_ONCE(&once, calcul_tables_16, NULL);
}

int
vips_col_sRGB2scRGB_16(int r, int g, int b, float *R, float *G, float *B)
{
	vips_col_make_tables_RGB_16();

	return vips_col_sRGB2scRGB(65536, vips_v2Y_16, r, g, b, R, G, B);
}

/* The matrix already includes the D65 channel weighting, so we just scale by
 * Y.
 */
#define SCALE (VIPS_D65_Y0)

/**
 * vips_col_scRGB2XYZ:
 * @R: Input scRGB value
 * @G: Input scRGB value
 * @B: Input scRGB value
 * @X: (out): Return XYZ colour
 * @Y: (out): Return XYZ colour
 * @Z: (out): Return XYZ colour
 *
 * Turn scRGB into XYZ.
 *
 * See also: vips_scRGB2XYZ().
 */
int
vips_col_scRGB2XYZ(float R, float G, float B, float *X, float *Y, float *Z)
{
	R *= SCALE;
	G *= SCALE;
	B *= SCALE;

	*X = 0.4124 * R +
		0.3576 * G +
		0.1805 * B;
	*Y = 0.2126 * R +
		0.7152 * G +
		0.0722 * B;
	*Z = 0.0193 * R +
		0.1192 * G +
		0.9505 * B;

	return 0;
}

/**
 * vips_col_XYZ2scRGB:
 * @X: Input XYZ value
 * @Y: Input XYZ value
 * @Z: Input XYZ value
 * @R: (out): Return scRGB colour
 * @G: (out): Return scRGB colour
 * @B: (out): Return scRGB colour
 *
 * Turn XYZ into scRGB.
 *
 * See also: vips_XYZ2scRGB().
 */
int
vips_col_XYZ2scRGB(float X, float Y, float Z, float *R, float *G, float *B)
{
	X /= SCALE;
	Y /= SCALE;
	Z /= SCALE;

	/* Use 6 decimal places of precision for the inverse matrix.
	 */
	*R = 3.240625 * X +
		-1.537208 * Y +
		-0.498629 * Z;
	*G = -0.968931 * X +
		1.875756 * Y +
		0.041518 * Z;
	*B = 0.055710 * X +
		-0.204021 * Y +
		1.056996 * Z;

	return 0;
}

/* Turn scRGB into sRGB. Return og=1 for out of gamut - rgb will contain an
 * approximation of the right colour.
 *
 * Return -1 for NaN.
 */
static int
vips_col_scRGB2sRGB(int range, int *lut,
	float R, float G, float B,
	int *r, int *g, int *b,
	int *og_ret)
{
	int maxval = range - 1;

	int og;
	float Yf;
	int Yi;
	float v;

	/* RGB can be NaN. Throw those values out, they will break
	 * our clipping.
	 *
	 * Don't use isnormal(), it is false for 0.0 and for subnormal
	 * numbers.
	 */
	if (VIPS_ISNAN(R) || VIPS_ISNAN(G) || VIPS_ISNAN(B)) {
		*r = 0;
		*g = 0;
		*b = 0;

		return -1;
	}

	/* Clip range, set the out-of-gamut flag.
	 */
#define CLIP(L, V, H) \
	{ \
		if ((V) < (L)) { \
			(V) = (L); \
			og = 1; \
		} \
		else if ((V) > (H)) { \
			(V) = (H); \
			og = 1; \
		} \
	}

	/* Look up with a float index: interpolate between the nearest two
	 * points.
	 *
	 * The +1 on the index is safe, see above.
	 */

	og = 0;

	Yf = R * maxval;
	CLIP(0, Yf, maxval);
	Yi = (int) Yf;
	v = lut[Yi] + (lut[Yi + 1] - lut[Yi]) * (Yf - Yi);
	*r = VIPS_RINT(v);

	Yf = G * maxval;
	CLIP(0, Yf, maxval);
	Yi = (int) Yf;
	v = lut[Yi] + (lut[Yi + 1] - lut[Yi]) * (Yf - Yi);
	*g = VIPS_RINT(v);

	Yf = B * maxval;
	CLIP(0, Yf, maxval);
	Yi = (int) Yf;
	v = lut[Yi] + (lut[Yi + 1] - lut[Yi]) * (Yf - Yi);
	*b = VIPS_RINT(v);

	if (og_ret)
		*og_ret = og;

	return 0;
}

int
vips_col_scRGB2sRGB_8(float R, float G, float B,
	int *r, int *g, int *b, int *og)
{
	vips_col_make_tables_RGB_8();

	return vips_col_scRGB2sRGB(256, vips_Y2v_8, R, G, B, r, g, b, og);
}

int
vips_col_scRGB2sRGB_16(float R, float G, float B,
	int *r, int *g, int *b, int *og)
{
	vips_col_make_tables_RGB_16();

	return vips_col_scRGB2sRGB(65536, vips_Y2v_16, R, G, B, r, g, b, og);
}

/* Turn scRGB into BW. Return or=1 for out of gamut - g will contain an
 * approximation of the right colour.
 *
 * Return -1 for NaN.
 */
static int
vips_col_scRGB2BW(int range, int *lut, float R, float G, float B,
	int *g, int *og_ret)
{
	int maxval = range - 1;

	float Y;
	int og;
	float Yf;
	int Yi;
	float v;

	/* CIE linear luminance function, see https://en.wikipedia.org/wiki/Grayscale#Colorimetric_(perceptual_luminance-preserving)_conversion_to_grayscale
	 */
	Y = 0.2126 * R + 0.7152 * G + 0.0722 * B;

	/* Y can be Nan. Throw those values out, they will break
	 * our clipping.
	 */
	if (VIPS_ISNAN(Y)) {
		*g = 0;

		return -1;
	}

	/* Look up with a float index: interpolate between the nearest two
	 * points.
	 *
	 * The +1 on the index is safe, see above.
	 */

	og = 0;

	Yf = Y * maxval;
	CLIP(0, Yf, maxval);
	Yi = (int) Yf;
	v = lut[Yi] + (lut[Yi + 1] - lut[Yi]) * (Yf - Yi);
	*g = VIPS_RINT(v);

	if (og_ret)
		*og_ret = og;

	return 0;
}

int
vips_col_scRGB2BW_16(float R, float G, float B, int *g, int *og)
{
	vips_col_make_tables_RGB_16();

	return vips_col_scRGB2BW(65536, vips_Y2v_16, R, G, B, g, og);
}

int
vips_col_scRGB2BW_8(float R, float G, float B, int *g, int *og)
{
	vips_col_make_tables_RGB_8();

	return vips_col_scRGB2BW(256, vips_Y2v_8, R, G, B, g, og);
}

/* Build Lab->disp dither tables.
 */
static void *
build_tables(void *client)
{
	int l, a, b;
	int t;

	for (l = 0; l < 64; l++) {
		for (a = 0; a < 64; a++) {
			for (b = 0; b < 64; b++) {
				/* Scale to lab space.
				 */
				float L = (l << 2) * (100.0 / 256.0);
				float A = (signed char) (a << 2);
				float B = (signed char) (b << 2);
				float X, Y, Z;
				float Rf, Gf, Bf;
				int rb, gb, bb;

				vips_col_Lab2XYZ(L, A, B, &X, &Y, &Z);
				vips_col_XYZ2scRGB(X, Y, Z, &Rf, &Gf, &Bf);
				vips_col_scRGB2sRGB_8(Rf, Gf, Bf, &rb, &gb, &bb, NULL);

				t = INDEX(l, a, b);
				vips_red[t] = rb;
				vips_green[t] = gb;
				vips_blue[t] = bb;
			}
		}
	}

	return NULL;
}

static void
vips_col_make_tables_LabQ2sRGB(void)
{
	static GOnce once = G_ONCE_INIT;

	VIPS_ONCE(&once, build_tables, NULL);
}

/* Process a buffer of data.
 */
static void
vips_LabQ2sRGB_line(VipsColour *colour, VipsPel *q, VipsPel **in, int width)
{
	unsigned char *p = (unsigned char *) in[0];

	int i, t;

	/* Current error.
	 */
	int le = 0;
	int ae = 0;
	int be = 0;

	vips_col_make_tables_LabQ2sRGB();

	for (i = 0; i < width; i++) {
		/* Get colour, add in error from previous pixel.
		 */
		int L = p[0] + le;
		int A = (signed char) p[1] + ae;
		int B = (signed char) p[2] + be;

		p += 4;

		/* Look out for overflow.
		 */
		L = VIPS_MIN(255, L);
		A = VIPS_MIN(127, A);
		B = VIPS_MIN(127, B);

		/* Find new quant error. This will always be +ve.
		 */
		le = L & 3;
		ae = A & 3;
		be = B & 3;

		/* Scale to 0-63.
		 */
		L = (L >> 2) & 63;
		A = (A >> 2) & 63;
		B = (B >> 2) & 63;

		/* Convert to RGB.
		 */
		t = INDEX(L, A, B);
		q[0] = vips_red[t];
		q[1] = vips_green[t];
		q[2] = vips_blue[t];

		q += 3;
	}
}

static void
vips_LabQ2sRGB_class_init(VipsLabQ2sRGBClass *class)
{
	VipsObjectClass *object_class = (VipsObjectClass *) class;
	VipsColourClass *colour_class = VIPS_COLOUR_CLASS(class);

	object_class->nickname = "LabQ2sRGB";
	object_class->description = _("convert a LabQ image to sRGB");

	colour_class->process_line = vips_LabQ2sRGB_line;
}

static void
vips_LabQ2sRGB_init(VipsLabQ2sRGB *LabQ2sRGB)
{
	VipsColour *colour = VIPS_COLOUR(LabQ2sRGB);
	VipsColourCode *code = VIPS_COLOUR_CODE(LabQ2sRGB);

	colour->coding = VIPS_CODING_NONE;
	colour->interpretation = VIPS_INTERPRETATION_sRGB;
	colour->format = VIPS_FORMAT_UCHAR;
	colour->bands = 3;

	code->input_coding = VIPS_CODING_LABQ;
}

/**
 * vips_LabQ2sRGB: (method)
 * @in: input image
 * @out: (out): output image
 * @...: %NULL-terminated list of optional named arguments
 *
 * Unpack a LabQ (#VIPS_CODING_LABQ) image to a three-band short image.
 *
 * See also: vips_LabS2LabQ(), vips_LabQ2sRGB(), vips_rad2float().
 *
 * Returns: 0 on success, -1 on error.
 */
int
vips_LabQ2sRGB(VipsImage *in, VipsImage **out, ...)
{
	va_list ap;
	int result;

	va_start(ap, out);
	result = vips_call_split("LabQ2sRGB", ap, in, out);
	va_end(ap);

	return result;
}
